Fuel System Plumbing

Based on good input from other builders in the RotorWay Owner's Group forum , I did change operation of the turbine's "Run Fuel" solenoid valve. This normally-closed solenoid valve came installed on the T-62 between the turbine fuel control assembly and the 6 turbine fuel injector nozzles. In this position, voltage must be supplied to hold the Run Fuel valve open to keep the turbine running. If the voltage drops below 3V, the Run Fuel valve will close and the turbine will flame out. This is O.K on a generater set but probably less desirable in a helicopter.

To avoid flameout from a possible momentary loss of electrical power, the valve was re-plumbed so that it can either maintain or release pressure from the fuel supply system. If the valve remains deenergized in its normally-closed position, it maintains fuel pressure in the supply tubing to the injector nozzles. Voltage must be supplied to open the solenoid valve to divert fuel/pressure away from the injector nozzles, which will cause the turbine flame to quit. Since this changes the original function, this valve might be better described as a "Divert Fuel" solenoid valve now.

(Note: You can click on these pictures to view in higher resolution.)

The former Run Fuel valve and existing 1/8" steel tubing from the turbine fuel control assembly to the fuel injector manifold were replaced with new steel tubing with a tee installed just after the fuel control assembly, shown here. 1/8" Tubing from the tee runs down to the new "Divert Fuel" solenoid valve location described below.

The 45o hose fitting shown is the supply connection to the turbine's fuel control assembly from the Boost Fuel pump. The 1/4" steel and temporary 3/8" polyethylene tubing also shown is a safety relief drain from the fuel control valve. The yellow connector to the right in this picture is from the turbine EGT thermocouple.

This picture shows the KISS 40 gallon fuel tank with the fuel fill plate installed. The fuel plate comes with a 2.25" 45o fill neck, a 1" vent neck and a 6AN 90o bulkhead fitting for the fuel pick-up tube inside the tank. A fuel shutoff valve is now installed on the hose from the fuel pick-up tube to the fuel filter, as shown below.

Here is the updated picture showing the manual fuel shutoff valve mounted on the tank and the fuel filter mounted in the recommended location. The fuel shutoff knob is located on the seat back just above the pilot's collective. The original Exec fuel tank support bracket provided a convenient spot to secure the actuator cable.

The fuel shutoff valve is an Earl's 3/8" FNPT x 6AN ball valve, with a small hole drilled in the handle for the actuator cable. The bend in the hose to the fuel filter allows for some vibration between the top of the fuel tank and the helicopter frame.

I needed to mount the Boost fuel pump somewhere, so I built a small aluminum containment box to mount the pump and the Divert Fuel solenoid valve, shown at left. I also used it to mount the two (boost pump and turbine pump) fuel pressure transducers too. While I was at it, it seemed like a good idea to mount the turbine oil pressure transducer and Low Oil Pressure switch here as well. This centralized all of these potential leak points into one location, which can contain and be quickly inspected for any small leaks or drips.

(Note: Not all of the fittings have been installed in the picture here.)

The fuel hoses from the filter and to the turbine enter and exit through the back of the box and connect to the boost pump inlet and outlet manifolds inside the box. The boost pump outlet is also connected with 1/8" tubing and fittings to the boost pump fuel pressure (0-15 psig) sensor.

The pump box also provided a good location to centralize all of the wiring connections on the left side of the helicopter, so I added this terminal box on top. More on this in the electrical section, later.

This drawing shows all of the plumbing connections and fittings used inside the pump box. The tee from the turbine fuel control assembly is shown mid-right in the drawing. As described above, the tee branches down with 1/8" tubing to the Divert Fuel solenoid valve installed in the pump box. A tee before the valve connects to the turbine fuel pressure (0-500 psig) sensor. The outlet from the Divert Fuel solenoid valve connects back into the boost pump inlet manifold. When the Divert Fuel valve opens, the high pressure fuel from the turbine fuel control assembly returns directly back into the boost pump inlet, which shuts down the turbine immediately.

The turbine oil pressure (0-100 psig) sensor and switch fittings are also shown. The 90o elbow fittings shown to the far right connect the tubing to the turbine gear case oil pressure port, where the oil switch was installed originally.

Here is a complete list of the plumbing fittings used for both the oil cooling and fuel systems, including suppliers, part numbers and pricing current as of 2006. If you find this helpful, please remember to donate generously to the author's personal beer consumption fund the next time you happen to meet him!